The intestinal mucosa is the biggest lymph organ in human body, which consists of the first line of defensive system with the respiratory mucosa and urinary mucosa. The intestinal mucosa is responsible to defend bacteria, viruses, dietary pathogens, non-steroid anti-inflammatory drug and so on. If the intestinal mucosal immune system is destroyed, the human will suffer many diseases such as infectious diseases,autoimmune diseases. Therefore, it plays an important part in physical health. T helper type 17 (Th17) cells different from Th1 cells and Th2 cells are a distinct lineage of T cells. The discovery of Th17 cells has ruined the constitutional pattern of Th1/Th2. Th17 cells, which are important parts of intestinal mucosal immune system,play critical roles in intestinal autoimmune diseases, tissue inflammation and the infection of various pathogenic bacteria. This paper will review the differentiation of Th17 cell and its function in intestinal mucosal barrier,intestinal autoimmune diseases and intestinal infectious diseases.